Particularly, such tracked automated roadwork machines include slipform pavers for producing a surface layer comprising concrete or asphalt material. Slipform pavers are construction machines with a characteristic finishing screed which serves, for example, for the installation of concrete or asphalt. The screed can also be formed with a characteristic profile, for example for the production of rails, channels or water grooves. Screeds are therefore produced for a wide variety of applications, i.e. with different screed profiles and screed widths.
The control of such road finishers can be effected by means of reference line scanning devices. A sensor scans the required direction and/or required height of a reference line, such as, for example, a tensioned wire; deviations from the required direction/required height are corrected by a regulating means. DE 101 38 563 discloses a wheel-type road finisher which automatically follows a reference line. In U.S. Pat. No. 5,599,134, scanning of a reference line is effected without contact, by means of ultrasonic sensors. However, this method of controlling a machine requires setting out of the area to be processed before the use of the construction vehicle and is very time-consuming and labor-intensive.
The method described in WO 2006/092441 A1 envisages mounting two masts with prisms on the crossbeams of a rigid machine frame formed from longitudinal beams and crossbeams and determining the distance and direction to the prisms by means of one or two tacheometers or total stations, and hence determining the position of the prisms or of the machine. These tacheometers or total stations are advantageously motor-powered and capable of automatically following the reflector. This document does not describe a method for aligning the track units to the machine frame, though.
For excellent straight line performance, tracked automated roadwork machines such as slipform pavers require their tracks to be accurately aligned to the surface processing unit (e. g. a roadwork unit such as a mould unit) of the machine. Machine manufactures and operators have developed many methods of aligning the tracks manually and with assistance of laser measurement tools.
When aligning tracks in this way, the following difficulties arise:                Accurately projecting the heading of the mould to the track, e. g. using a string.        Measuring the track against the projected string alignment to millimetre precision on rough ground.        Communicating millimetre rotational movement commands from the person looking at the track to the operator of the machine.        Moving the tracks with the ultra-fine movements that are required to align the track.        
Also, on several surfaces, when the tracks are pivoted the mould unit will often move slightly. This requires an iterative process of aligning the track to the surface processing unit, then re-checking the surface processing unit's heading, as it unintentionally might have moved, realigning the track, and so forth.